[Wien] negative grr values in mBJ calculation causing lapw0 to fail

[Neil Johnson]

Hello Dr. Tran,

I believe I have located the problem. The SCF cycle did not fully converge before the density gradient was calculated. Running SCF to full convergence should ameliorate this issue.

Thank you,
-Neil Johnson, B.Sc.



On 12-07-11 1:22 AM, tran at theochem.tuwien.ac.at wrote:
> In principle, GRR should not be negative because it is the average of
> |??|/? (note that it's the norm) in the unit cell volume.
> In output0_grr, there is
> TOTAL=  *************
> for the PLANE WAVE CONTRIBUTION, which means that the problem comes from
> the interstitial region. I would guess that this comes from some numerical
> instabilities.
>
> Such problems car arise close to the nucleus of very atoms or in regions
> of space with low electron density. Is it the case in your system?
> For the moment, I can not say much more.
>
> F. Tran
>
> On Tue, 10 Jul 2012, Neil Johnson wrote:
>
>> Hello all,
>> I am attempting to perform an mBJ calculation using the steps listed in sec
>> 4.5.8 of the user's manual. However, lapw0 keeps failing in the final scf
>> cycles after switching to IXC=28. We tracked the problem down to a negative
>> GRR (??/? = -36.0544), the square root of which is taken to calculate "c for
>> IXC=28" in lapw0. Taking the square root of a negative number is generally
>> frowned upon, and the program spits out a lot of "NaN"s before failing.
>>
>> Has anyone experienced this problem before, or know what would cause lapw0
>> -grr to produce a negative GRR value?
>>
>> I've posted the output0 and output0_grr files to
>> http://homepage.usask.ca/~nwj781/lapw0/
>> <http://homepage.usask.ca/%7Enwj781/lapw0/> for reference. Thanks!
>>
>> Cheers,
>>
>> Neil Johnson
>> University of Saskatchewan
>> Saskatoon, Canada
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>>
>>
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